Effect of β-cyclodextrin on antioxidant activity of coumaric acids

Inclusion complexes of o-, m- and p-coumaric acid (CA) with β-cyclodextrin (βCD) were prepared in stoichiometric ratios (1:1) and stability constants and antioxidant activity of the complexes were studied. The apparent stability constants in aqueous solution of 0.39 × 10³ M⁻¹, 2.81 × 10³ M⁻¹ and 49 × 10³ M⁻¹ for o-, m- and p-CA complexes, respectively, were determined by phase solubility tests. Different analytical techniques (IR, MS) in combination with different solvent washing procedures, were used for confirmation of the nature of the inclusion complexes. Dioxan was a suitable solvent for removal of only free CA and CA adsorbed on the surface of the βCD, while methanol removed absorbed, included and free CA from the complexes. In the case of o- and m-CA–βCD complexes, antioxidant activity was significantly increased while, in p-CA–βCD, it remained unchanged. The impact of complex structure on antioxidant activity of CA isomers was clarified.     

Study of digital systems for the automatic phase lock of a sequential resonance inverter

The digital phase system for the automatic phase lock of a resonance inverter that feeds into an inductor system is studied. The transient processes that develop if the circuit frequency changes are considered. A method for calculating the dead zone of the relay element of a phase detector, which enables free oscillations of the stabilized difference of the current and voltage phases to be removed, is considered. Dependences of the dead zone on the Q factor of the oscillatory circuit and the step of frequency tuning are derived     

Investigation of the effect of control action parameters on characteristics of a phase-locked-loop frequency control system of a consecutive resonance inverter

Digital phase-locked-loop frequency control (PLFC) systems of a consecutive resonance inverter with the different phase detector characteristics are considered. The efficiency of phase detector signal digital filtration for enhancing the control accuracy and multilevel characteristic of a digital phase detector (DPD) to increase the maximum switching frequency is shown. Using the example of a proportional DPD, dependences for determining the control action parameters that yield adequate characteristics for a PLFC system are obtained.     

Polyamide 6 composite fibers with incorporated mixtures of melamine cyanurate,carbon nanotubes,and carbon black

Polyamide 6 (PA6) composite filament yarns were produced by the simultaneous incorporation of melamine cyanurate (MeCy) with multiwalled carbon nanotubes (CNTs) and carbon black (CB) into a composite matrix in a melt-spinning process. The results show that the simultaneous incorporation of MeCy with CNTs or CB additives provided filaments with a uniform black color. Tensile analysis confirmed that a reinforcing effect was achieved when CB was used, whereas the CNTs induced a reducing effect on the filament tenacity. With regard to the burning behavior, the flame-retardant action of MeCy was preserved in the presence of CB but was significantly hindered when used in combination with CNTs. These results indicate that the mixture of MeCy and CB was much more compatible for the production of reinforced PA6 composite filaments with increased thermal stability and improved flame retardancy over those of the MeCy and CNTs. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47007.     

Gas Responsive Nanoswitch: Copper Oxide Composite for Highly Selective H2S Detection

A nanocomposite material based on copper(II) oxide (CuO) and its utilization as a highly selective and stable gas‐responsive electrical switch for hydrogen sulphide (H₂S) detection is presented. The material can be applied as a sensitive layer for H₂S monitoring, e.g., in biogas gas plants. CuO nanoparticles are embedded in a rigid, nanoporous silica (SiO₂) matrix to form an electrical percolating network of low conducting CuO and, upon exposure to H₂S, highly conducting copper(II) sulphide (CuS) particles. By steric hindrance due to the silica pore walls, the structure of the network is maintained even though the reversible reaction of CuO to CuS is accompanied by significant volume expansion. The conducting state of the percolating network can be controlled by a variety of parameters, such as temperature, electrode layout, and network topology of the porous silica matrix. The latter means that this new type of sensing material has a structure‐encoded detection limit for H₂S, which offers new application opportunities. The fabrication process of the mesoporous CuO@SiO₂ composite as well as the sensor design and characteristics are described in detail. In addition, theoretical modeling of the percolation effect by Monte‐Carlo simulations yields deeper insight into the underlying percolation mechanism and the observed response characteristics.     

Evaluation of automobile service performance using laboratory testing

A methodology is presented to evaluate martensitic advanced high-strength steels in auto service. There was essentially no influence of hydrogen for (i) linearly increasing stress tests of specimens with hydrogen contents much greater than for automobile service, and (ii) for tensile tests with simultaneous hydrogen charging and with a substantial hydrogen content. These results allow evaluation of the hydrogen influence for the tested steels for auto service. In contrast, electrochemically hydrogen charged martensitic advanced high-strength steels showed an influence of hydrogen on mechanical properties, manifest as (i) a decrease in yield strength, by hydrogen enhanced macroscopic ductility, and (ii) a change of the micro-fracture mode, by hydrogen-assisted micro-fracture.     

Characterising heave,pitch, and roll motion of road vehicles with principal component and frequency analysis

For the great majority of transport vehicles, the magnitude of the heave vibration is generally more severe than pitch and roll. Consequently, the measurement, analysis, and simulation of the vehicle vibrations have been focused on vertical vibration. Despite this, it is now being increasingly recognised that the combination of heave, pitch, and roll vibratory motion can induce more severe damage to shipments than vertical vibration alone. Although the pitch and roll motion of road vehicles can now be readily measured, there is little information on how to analyse the data to produce meaningful statistical relationships between the three variables. This paper builds upon previous work that showed that there is some correlation between pitch, roll, and heave motion and that these relationships are dependent on vehicle geometry, including payload mass, centre of mass, vehicle roll centre, and moments of inertia as well as vehicle speed and the road surface. In this paper, data from a range of quasi‐controlled experiments, which involved driving vehicles at constant‐speed on selected roads, were analysed using principal component analysis as well as frequency domain analysis to reveal the relationship between heave, pitch, and roll motion. This was undertaken for a variety of vehicle speeds and routes in order to establish if they influence pitch and roll response. Results are presented in the form of distribution functions, statistical coefficients, and frequency response functions, all of which are useful for helping to define parameters for the simulation of complete, three‐axis vibrations using multi‐axis vibration test systems.     

Preparation of Macroscopic Block‐Copolymer‐Based Gyroidal Mesoscale Single Crystals by Solvent Evaporation

Properties arising from ordered periodic mesostructures are often obscured by small, randomly oriented domains and grain boundaries. Bulk macroscopic single crystals with mesoscale periodicity are needed to establish fundamental structure–property correlations for materials ordered at this length scale (10–100 nm). A solvent‐evaporation‐induced crystallization method providing access to large (millimeter to centimeter) single‐crystal mesostructures, specifically bicontinuous gyroids, in thick films (>100 µm) derived from block copolymers is reported. After in‐depth crystallographic characterization of single‐crystal block copolymer–preceramic nanocomposite films, the structures are converted into mesoporous ceramic monoliths, with retention of mesoscale crystallinity. When fractured, these monoliths display single‐crystal‐like cleavage along mesoscale facets. The method can prepare macroscopic bulk single crystals with other block copolymer systems, suggesting that the method is broadly applicable to block copolymer materials assembled by solvent evaporation. It is expected that such bulk single crystals will enable fundamental understanding and control of emergent mesostructure‐based properties in block‐copolymer‐directed metal, semiconductor, and superconductor materials.     

Compensatory mechanisms in erythrocyte lipids in patients with atherosclerosis

The quantitative coposition of phospholipids and fatty acids of erythrocytes was investigated in patients with atherosclerosis. It was stated that the erythrocyte lipids of atherosclerotic patients contained smaller quantitities of phosphatidylcholine and phosphatidylinositol, a significantly larger quantity of sphingomyelin, and higher sphingomyelin/phosphatidylcholine and cholesterol/phospholipid ratios. The existence of compensatory changes was stated, which was evident in the reduction of palmitic and stearic acids and the increase of linoleic and eicosatrienoic acids in erythrocyte phospholipids. These changes in fatty acid composition probably cause minimal changes in the membrane fluidity indiced by an increased cholesterol/phospholipid and sphingomyelin/phosphatidylcholine ratios. This paper was the first evidence of occurrence of those changes in erythrocytes during spontaneous atherosclerosis in human